3rd UF Water Institute Symposium Abstract

Submitter's Name Xiaolin Liao
Session Name Posters - Nutrient Dynamics and Enrichment Impacts in Aquatic Ecosystems 1
Category Nutrient dynamics and enrichment impacts in aquatic ecosystems
Poster Number 31
Author(s) Xiaolin Liao,  Soil and water science department (Presenting Author)
  Patrick Inglett,  soil and water science department, UF
  Cassandra Medvedeff, soil and water science department, UF
  Ben Hogue, soil and water science department, UF
  Kanika Inglett, soil and water science department, UF
  Seasonal patterns of periphyton nitrogen fixation in seasonally-flooded calcareous wetlands of the Florida Everglades
  Fire is an important driver in various ecosystems and can affect nutrient cycling by changing the form, distribution and amount of nutrients However, nitrogen (N) cycling in response to fire is not well understood, especially for ecosystems like the oligotrophic wetlands. In this study, a restored wetland (restored in 2000, high phosphorus) and a native calcareous wetland (reference site, low phosphorus) were burned on 4th May, 2010 in the Hole-in-the-Donut (HID) of Florida Everglades, where farmed marl prairie wetlands have been restored through complete soil removal to reduce nutrient levels. In each site, we had two pairs of 30m by 30m burn and control plots set. Soil properties were measured to evaluate the immediate (2 days), short (1month) and long time (around 1 year) changes of soil nitrogen cycles after the fire. Results showed that immediately after the fire, extractable nitrate/nitrite (NOX-N) and ammonia (NH4-N) elevated in the burn plots compared to the control plots in both restored and reference site. After one year of the fire, the extractable NOX-N and NH4-N gradually returned to the control level. These results suggest that the inorganic nitrogen would release to the soil very rapidly after the fire, but with the time, the nutrient uptake by plants would deplete soil available nitrogen. The N-related enzyme (Leucine-aminopeptidase, LAP and N-acetyl-β-D-glucosaminidase, NAG) were highly correlated with nitrogen mineralization, and their response to fire varied with different time and sites. An increase of LAP: NAG ratio was also observed in the burn plots immediately after the fire, indicating the possible changes of microbial community after the fire. We also saw a 20% higher denitrification rate immediately after the fire in the burn plots but after 1 month it decrease to the control level. The correlation between the denitrification and the NOX-N suggested the denitrification was not only caused by the increased NOX-N, the charcoal mechanism would be a possible reason. The low-P reference site responded to the fire much greater than the high-P restored site, indicating the P released by the fire in the reference site would fuel the nitrogen cycle.